1. Field of the Invention
The present invention relates to a thermal transfer recording method for recording an image on a recording medium by transferring ink from an ink sheet, and a recording apparatus utilizing such recording method.
Such thermal transfer recording apparatus may include a facsimile apparatus, an electronic typewriter, a copying apparatus, a printer or the like.
2. Related Background Art
In general, the thermal transfer printer employs an ink sheet containing thermofusible (or thermosublimable) ink coated on a substrate film, and achieves image recording by selectively heating this ink sheet with a thermal head corresponding to image signals, thereby transferring the fused (or subliming) ink onto a recording sheet. In such thermal transfer recording, the interval from the end of recording of a line to the start of recording of a next line may be extended. In such case, in order to prevent complete cooling of the thermal head, it is already conceived to effect so-called auxiliary recording, in which the thermal head is activated with the same recording data as in the preceding line but with an energy insufficient for transfer recording. Such conventional auxiliary recording will be explained further in the following, with reference to FIG. 7.
FIG. 7 shows the timing of image recording with a line thermal head, wherein T101-T103 indicate the timings of print commands for instructing the start of printing operation; T201-T203 indicate the start timings of transfer of the ink sheet and the recording sheet; 70 and 71 indicate pre-heating of the preceding line to be executed immediately before the actual recording; and 72-74 indicate the timings of actual image recording of one line each. The image recording 74 is conducted, without preheating, immediately after the image recording 73, as a print start command (timing T103) is entered in the course of said image recording 73.
L indicates the moving distance of the recording sheet and the ink sheet, and a curve 75 shows the moving state thereof as a function of time. The length of a recorded line is indicated by l. After the image recording 72 of a line, the preheating 71 with the data of said line is conducted prior to the next image recording 73, if the print command therefor is entered (timing T102) within a predetermined period of time after recording 72. This pre-heating is carried out to prevent the adhesion of the ink sheet and the recording sheet, resulting from solidification of the ink of the ink sheet when the thermal head is cooled.
After the completion of pre-heating 71, the transportation of the ink sheet and the recording sheet is started at the timing T202.
However, as indicated by an arrow 76, the ink sheet and the recording sheet scarcely move at the start of recording, and the transportation of the recording sheet by a line length l in fact takes place after a line recording time, corresponding to an arrow 77. Thus, in the conventionally conceived structure, though measures are taken for preventing the adhesion of the recording sheet and the ink sheet thereby improving the start characteristics of transportation of said sheets, the effect of such measures may not be fully exploited. Also there may result a gap (white streak) between the lines, because the image recording is already over when the recording sheet is transported by the line pitch l.